KR101467041B1 - Manufacturing method of crank shaft - Google Patents

Abstract

The present invention relates to a crankshaft manufacturing method, and more particularly, to a crankshaft manufacturing method capable of reducing the occurrence of cracks in a fin portion.
The present invention relates to a method for manufacturing a crankshaft by forging a rod material, the method comprising: a buster mold having a forming groove corresponding to a primary shape set in an intermediate form of a rod material and a crankshaft in a range capable of forming in a rod material; A blocker mold having an intermediate shape of a shape and a crankshaft shape and having a molding groove corresponding to a secondary shape set in a range capable of forming the primary shape, and a finisher mold having a molding groove corresponding to a crankshaft shape, Wherein the primary shape and the secondary shape are set so as not to be exposed to the surface of the fin portion of the crankshaft in which the center seated stone is manufactured.

Description

Technical Field [0001] The present invention relates to a method of manufacturing a crankshaft,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crankshaft manufacturing method, and more particularly, to a crankshaft manufacturing method capable of reducing the occurrence of cracks in a fin portion.

Steels used in crankshafts have been developed as non-tempered steels in which quenching heat treatment is omitted from heavy quenching & tempering materials.

In order to prevent deterioration of processability due to high hardness, non - nitrided steel was tried to induce the formation of MnS in the molten steel and to achieve a pleasant smell.

MnS in the steel acts as a position of micro crack in the base to lower the processing force and shorten the chip shape, thereby improving the workability.

However, when MnS segregated at the center of the raw material is located on the fin portion of the crankshaft, cracks can be caused at high frequencies, and in this case, the engine can be disassembled.

Related Prior Art Korean Unexamined Patent Publication No. 10-2012-0032966 (published on Apr. 6, 2012) entitled " High-strength, high-strength, non-tempered steel for a crankshaft with excellent fatigue strength and a manufacturing method thereof.

SUMMARY OF THE INVENTION An object of the present invention is to provide a crankshaft manufacturing method capable of improving the durability and reliability of a crankshaft by preventing a center seizing rod that causes a crack from being present on the outer surface of a pin portion of the crankshaft.

The present invention relates to a method for manufacturing a crankshaft by forging a rod material, the method comprising: a buster mold having a forming groove corresponding to a primary shape set in an intermediate form of a rod material and a crankshaft in a range capable of forming in a rod material; A blocker mold having an intermediate shape of a shape and a crankshaft shape and having a molding groove corresponding to a secondary shape set in a range capable of forming the primary shape, and a finisher mold having a molding groove corresponding to a crankshaft shape, Wherein the primary shape and the secondary shape are set so as not to be exposed to the surface of the fin portion of the crankshaft in which the center seated stone is manufactured.

In this case, if it is predicted that the center segregation band is exposed on the surface of the fin portion of the crankshaft through the molding analysis, the volume ratio of the primary shape is adjusted, and the reduction ratio in the primary shape Is increased.

The adjustment of the volume ratio of the primary shape is performed so as to increase the volume moving to the flash portion. The volume ratio of the primary shape is controlled by adjusting the center of the bar material to 2.5-3.0 gt; mm. < / RTI >

The present invention also provides a bumper mold having an intermediate shape between a bar material and a crankshaft and having a forming groove corresponding to a primary shape set in a range capable of being formed in a bar material and a bumper mold having an intermediate shape between the primary shape and the crankshaft, A blocker die having a forming groove corresponding to a secondary shape set in a range capable of forming in a car shape and a finishing die having a forming groove corresponding to a crankshaft shape, Wherein the crankshaft does not exist inside the crankshaft.

A method of manufacturing a crankshaft according to the present invention is a method in which a primary shape and a secondary shape are changed through a molding analysis so that a center segregation band does not exist inside a crankshaft fin portion and can be discharged and removed to a flash portion, Thereby improving the durability and reliability of the battery.

1 is a view showing the position of a center segregation zone of a cross section of a crankshaft.
2 is a view showing a state in which the bar material is forged with a buster mold;
Fig. 3 is a view showing a state where a material passed through a buster mold is forged with a blocker mold.
Fig. 4 is a view showing a state in which a material passed through a blocker mold is forged with a finisher mold.
5 is an exemplary view showing a flash portion in which the center seats are exposed to the pin portion,
6 is a view showing a flash unit in which the center seats are removed to the flash unit by modifying the buster mold.

Hereinafter, a method of manufacturing a crankshaft according to an embodiment of the present invention will be described in detail with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to achieve them, will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

Like reference numerals refer to like elements throughout the specification.

In the drawings, it is to be noted that the sizes of the constituent elements of the invention are exaggerated for clarity of description, and when it is described that any constituent element is present inside or connected to another constituent element, The element may be installed in contact with the other element, may be installed at a predetermined distance from the element, and may be provided with a third element for fixing or connecting the element to the other element, The description of the means may be omitted.

1 is a view showing the position of a center segregation zone of a cross section of a crankshaft.

As shown, the crankshaft has a shape refracted in both directions in the rotational center axis, and a pin portion is formed at a position spaced apart from the rotational center axis.

When a crankshaft is manufactured by forging a rod, the center segregation zone located at the center of the rod varies depending on the deformation history of the material.

In the drawing, the portion indicated by the dotted line indicates the position of the center seized stone.

The crankshaft is subjected to a forging process, followed by a cutting process and a high frequency surface treatment. When the center segregation band is distributed as shown in the figure, the center segregation is expected to be exposed to the surface of the fin by cutting do.

When the center seats are exposed to the surface of the fin portion, micro cracks may occur in the MnS of the center seats during the high frequency surface treatment. Micro cracks generated in the fin portions are expanded due to repetitive load caused by the connecting rod during operation of the engine, It can cause a disconnection.

Fig. 3 is a view showing a state in which a material roughed by a buster mold is forged by a blocker mold, Fig. 4 is a view showing a state in which a material roughed by a blocker mold is forged Fig.

The crankshaft is produced by forging and shaping a bar material.

Once the final shape of the crankshaft is designed, intermediate shapes of the crankshaft and the bar are determined from the forging to the extent that the crankshaft can be formed.

Generally, the crankshaft is forged through the third forging,

Buster mold for the first forging of the bar, Blower mold for the second forging of the material which passed through the buster mold, and Finisher mold for the final forging of the material passed through the blocker mold.

The shape formed by the buster mold is referred to as a primary shape, and the shape formed by the blocker mold is referred to as a secondary shape.

The primary shape is set in a range that can be formed by forging by applying pressure within a set range in the bar material in consideration of the strength and strain rate of the material,

The secondary shape is a range that can be formed in the primary shape in the same manner and is set so that the crankshaft shape can be formed from the secondary shape.

After the shape of the crankshaft is determined, the diameters of the primary shape, the secondary shape, and the raw material bar are determined.

When the shape of the intermediate forming process is determined, the metal flow is subjected to a forming analysis by a finite element analysis method to predict a change in the position of the center of the bar.

Since the center seated rod is located on the inner side of about 5 mm in diameter from the center of the rod, it is possible to predict whether the center seated rod is positioned on the surface of the fin of the crank shaft through the above-described forming analysis.

As a result, when the center seized rod is located on the surface of the fin portion of the crankshaft, it is necessary to correct the primary shape.

At this time, the correction of the primary shape proceeds in such a direction that the center seated stone can be moved to the flash unit.

That is, by setting the volume distribution of the portion to be finned and the portion to be exited to the flash portion in the primary shape differently, it is possible to discharge the center seized stone to the flash portion in the final shape.

More specifically, increasing the reduction rate of the boundary between the portion to be added to the pin and the portion to be exfoliated to the flash portion in the primary shape causes a larger amount of material to be pushed to the side of the flash portion. As a result, Resulting in moving to the flash unit side.

At this time, it is preferable to make it 2.5-3.0 mm apart from the flash portion interface at the center of the bar material. When the center of the bar is less than 2.5 mm, there is a possibility that the center segregation band is exposed to the surface of the fin portion after cutting, and it is not necessary to correct the center segregation band to be discharged in excess of 3.0 mm.

FIG. 5 is an exemplary view showing a flash unit in which the center seismic band is exposed to the fin, and FIG. 6 is a view showing a flash unit in which the center seismic band is discharged to the flash unit by modifying the buster mold.

For example, if the center seats are exposed to the pin portion of the crankshaft in this case, the center seats are discharged to the flash portion through the modification of the buster mold, The shape of the flash portion due to the modified mold is shown as an increase in the length of the outer flash portion of the pin portion as shown in FIG.

The increase in the length of the flash part means that a larger amount of material has been discharged to the flash part side, from which the center of the material has moved toward the flash part side.

With the above-described method, it is possible to manufacture a crankshaft in which the center seizing rod is not present inside the fin portion of the crankshaft.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. It will be understood that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (5)

A method for manufacturing a crankshaft by forging a rod,
A buster mold having an intermediate shape between a bar and a crankshaft and having a forming groove corresponding to a primary shape set in a range capable of being formed by forging in consideration of the strength and strain of the material;
A blocker mold having an intermediate shape between the primary shape and the crankshaft shape and having a forming groove corresponding to a secondary shape set in a range capable of being formed in the primary shape by forging in consideration of the strength and strain of the material;
And then finishing the mold with a finishing die having a forming groove corresponding to the crankshaft shape,
If it is predicted that the center seats are exposed to the surface of the fin portion of the crankshaft through the molding analysis,
The volume ratio of the primary shape is adjusted so that the volume moving to the flash unit is increased, the primary shape is set so that the center seated stone can escape to the flash unit to increase the reduction rate, and the crankshaft And the secondary shape is set so as not to be exposed to the fin surface of the crankshaft.
delete delete The method according to claim 1,
The volume ratio adjustment of the primary shape
So that the volume center of the bar can be displaced by 2.5 to 3.0 mm from the interface of the flash part.
delete

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